We are investigating the capacity of the retina to carry out the biosynthesis of its mannose-containing glycoproteins, with special emphasis being placed on the biosynthesis of the saccharide moieties of the glycoprotein, rhodopsin. We are studying the biosynthesis and properties of polyisoprene-mannose-containing lipids by the retina, and are investigating their role in the biosynthesis of rhodopsin. These studies are being carried out primarily with preparations from the retina of the embryonic chick and with rat and bovine retinas. We have demonstrated the existence of multiple forms of rhodopsin which differ from one another in terms of their isoelectric points. We are investigating other chemical and biochemical properties of these several species of rhodopsin.